Street sweepers are capable of dislodging and picking up dirt and debris from the street, typically by means of a brush, and conveying the dirt to a hopper for storage. When the hopper is to be dumped, it is desirable for the entire hopper to be tipped so that contents slide out from the hopper by gravity into a garbage dump or other storage area.
In the prior art, a street sweeper manufactured by Mobile Athey Inc. utilizes a hopper that is elevatable by a scissor type lift, so that the hopper can be elevated over the side of a dumpster, for example. The hopper can be tilted sideways for dumping. Such a structure is of substantial complexity, having many moving parts. Typically, five scissors stages are required, along with four pressure cylinders for the hydraulic lift system, all of which is rather expensive and complex. Additionally the hopper at the top of its elevation on such a scissor type lift is less rigid in its support, being subject to significant oscillation and bending, which is clearly undesirable and, if the oscillations are taken to an extreme, can result in damage to the mechanism.
By this invention, an improved street sweeper with an elevatable hopper is provided, in which a more reliable, simpler mast-type hopper lift system is provided. The street sweeper of this invention is capable of elevating a fully loaded hopper with much less oscillation and flexing of the hopper in its elevated condition, the entire lift system being more rigid and stronger than in the prior art. Additionally, the lift system used in this invention is simpler, less expensive, and more reliable than the system of the prior art.
Additionally, while it is desirable for a street sweeper to have a relatively rigid suspension system for its wheels as it proceeds along in the street sweeping mode at typically a low rate of speed, it would be desirable for a street sweeper to have a softer, more resilient wheel suspension for higher speed road travel. The more rigid suspension system is desirable so that the brush and dust collector members will not bounce on the road during the sweeping operation as the street sweeper moves forward. At the same time, when the street sweeping members are lifted out of the way and the sweeper vehicle is travelling at normal road speeds, a resilient suspension is more desirable.
Similarly, in street sweepers which utilize a mechanical conveyor such as a conveyor belt for carrying dirt from the dirt collection means upwardly into the hopper, it is desirable for the conveyor to be mounted on a resilient suspension system, so that the bottom of the conveyor can resiliently conform to irregularities in the road along which it travels during street sweeping processes. Thus, the conveyor will flex upwardly when a bump is encountered, and fall downwardly into depressions, to conform to the road surface for better street sweeping capability.
Additionally, during normal speed road travel, it is desired for the conveyor to be lifted out of the way so that its road engaging end does not contact the road in that circumstance.
By this invention, a novel suspension system for street sweeper conveyors is provided to accomplish the above purposes.
Additionally, it is desirable for the rotary broom that is usually found on a street sweeper to engage the road in a resilient manner during operation, in which the pressure of the broom against the road is relatively constant. This provides improvements over a rigid suspension of the broom in that, as the bristles of the of the broom wear, a pressure-dictated suspension system will spontaneously adjust the broom to the appropriate height at which the pressure of the broom against the road is of a predetermined value, so that the broom automatically compensates for wearing of bristles during operation.
By this invention, all of the above features and advantages may be incorporated into a street sweeper, to provide significantly improved street sweeping operation with simplified, more reliable structure and reduced cost.